1. Field of the Invention
The present invention is directed to a hydrodynamic clutch arrangement, particularly a torque converter or fluid coupling, including a housing arrangement, a turbine wheel provided in the housing arrangement, and a lockup clutch arrangement by which a torque transmitting connection can be produced selectively between the turbine wheel and the housing arrangement. The lockup clutch arrangement includes at least two friction members which are rotatable with one of the housing arrangement and turbine wheel, at least one counter-friction member which is rotatable with the other of the housing arrangement and turbine wheel and which is interposed between two friction members and can be brought into contact with friction surface regions of the friction members in friction surface regions of the counter-friction member.
2. Description of the Related Art
U.S. Pat. No. 6,293,380 discloses a hydrodynamic clutch arrangement in the form of a hydrodynamic torque converter. In this hydrodynamic torque converter, two friction members in the form of plates similar to friction disks are coupled with the turbine wheel for common rotation. These two plates lie between a clutch piston and an area of the housing arrangement. Friction surfaces with which corresponding friction surfaces at the two plates can be brought into contact are provided at the clutch piston and also at this area of the housing arrangement. Further, as an additional counter-friction member coupled with the housing arrangement for common rotation, a friction plate constructed in the manner of a ring disk is provided between the two friction members which are constructed as plates. This friction plate is pressed between the two plate-like friction members when the clutch piston is displaced. Friction facings are provided at the two friction members or plates at both sides, so that these friction facings can enter into frictional contact with the clutch piston or housing arrangement on the one hand and with the counter-friction member constructed as a ring disk on the other hand. Ultimately, this means that, in the area the friction members, the friction surface regions provided in this area are formed by surface regions of the friction facings, while in the area of the counter-friction members, i.e., the clutch piston, the structural component part which is constructed in the manner of a ring disk and located between the two friction members, and the housing arrangement, metal surfaces form the friction surface regions.
The basic problem in a hydrodynamic clutch arrangement constructed in this way is in that a comparatively large thermal load occurs in case of friction heat occurring in slip operation of the lockup clutch arrangement, particularly in the counter-friction element which is constructed in the manner of a ring disk and is located between the two plate-like friction elements. This is due to the fact that, first, this friction acts upon this structural component part over a large portion of its surface, so that there is only poor conduction of heat away from this structural component part. Also, its dimensions, particularly its thickness, are appreciably smaller, for example, than the clutch piston or housing arrangement in the area acted upon by friction, so that heat distribution in a larger volume area is also not possible in this case. Due to the nonuniform heating of the components or component areas in question during friction operation, local overheating can occur, so that damage to or failure of the entire lockup clutch arrangement can be caused in this overheated area in spite of the fact that other areas are not thermally overloaded.
U.S. Pat. No. 5,211,270 discloses a hydrodynamic clutch arrangement with a lockup clutch arrangement in which a counter-friction element which is constructed in the manner of a ring disk is connected with the housing arrangement so as to be rotatable. This counter-friction element constructed as a ring disk is located between a friction element which is constructed in the manner of a plate and a clutch piston which, in this case, is to be considered as an additional friction element which is rotatable in common with the plate-like friction element. In this arrangement also, the above-mentioned problem of local overheating due to comparatively poor capacity to dissipate heat can arise in the counter-friction element which is constructed as a ring disk and which is not provided with friction facings.
DE 198 26 351 discloses a hydrodynamic clutch arrangement in the form of a hydrodynamic torque converter in which the clutch piston as well as an abutment element are connected with the housing arrangement so as to be rotatable. Two plate-shaped friction members which have friction facings and are coupled with the turbine wheel for common rotation are located between these two elements. A counter-friction member which is constructed as a ring disk is located between these two friction members and, together with the abutment element and the clutch piston and another counter-friction member which is constructed as a ring disk and directly adjoins the clutch piston, is rotatable with the housing arrangement. In this arrangement, particularly in the region of the counter-friction member which is constructed as a ring disk and is interposed between the two friction members, there is a risk of local overheating due to the comparatively poor heat dissipation from this region.
It is the object of the present invention to further develop a hydrodynamic clutch arrangement of the type described above in such a way that the risk of local overheating due to heat generated in the region of the lockup clutch arrangement can be reduced or eliminated.
According to the invention, an outer radius of the counter-friction member body is in a ratio of 1.1:1 to 1.5:1 to an outer radius of the friction surface region or regions provided at the latter and/or an inner radius of the counter-friction member body is in a ratio of 0.4:1 to 0.8:1 to an inner radius of the friction surface region or regions provided at the latter.
By providing a counter-friction member having comparatively large surface regions which go beyond its friction surface region or regions and which are not acted upon by friction, wherein fluid present in a hydrodynamic clutch arrangement of this type flows around these large surface regions, friction heat that may be generated can be carried away from the counter-friction member in an improved manner so that the risk of local overheating can be prevented.
Further, in the hydrodynamic clutch arrangement according to the invention, a toothed rotational coupling formation which is in a rotational driving engagement with a rotational coupling formation provided at the housing arrangement is preferably provided at the radial inner area of the counter-friction member body. In this case, the at least two friction members are coupled with the turbine wheel so as to be rotatable.
In order to be able to generate the desired forces when frictional interaction is produced, it can further be provided that friction facings are provided at the at least two friction members and can be brought into contact at the friction surface regions of the counter-friction member.
According to another feature of the present invention, the above-stated object is met by a hydrodynamic clutch arrangement, particularly a torque converter or fluid coupling, comprising a housing arrangement, a turbine wheel provided in the housing arrangement, and a lockup clutch arrangement by which a torque transmitting connection can be produced selectively between the turbine wheel and the housing arrangement. The lockup clutch arrangement comprises at least two friction members which are rotatable with a subassembly comprising one of the housing arrangement and turbine wheel, at least one counter-friction member which is rotatable with the other subassembly comprising the other of the housing arrangement and turbine wheel and which is interposed between two friction members. The counter-friction member can be brought into contact with friction surface regions of the friction members in friction surface regions of the counter-friction member, by means of a pressing element.
According to the invention, it is further provided that the counter-friction member has, at least partially, a thickness that is at least as great as the thickness of the pressing element in its region acting upon the friction members and counter-friction members and/or that the counter-friction member has, at least partially, a thickness that is at least as great as the thickness of an abutment member, wherein the friction members and counter-friction members can be pressed between the abutment member and the pressing element.
Also, by providing a comparatively thick counter-friction member whose thickness corresponds at least to the thickness of other subassemblies involving friction, it can likewise be ensured that the heat energy generated in the region of the counter-friction member is distributed in a comparatively large volume area and is accordingly conducted off comparatively quickly from the surface regions and can be carried off into the surroundings in an improved manner.
It is noted that, of course, this feature can be combined with the preceding feature relating to the dimensioning of the radial extension of the counter-friction member.
In a hydrodynamic clutch arrangement constructed in the manner described above, the friction members can preferably be rotatable with the turbine wheel and the counter-friction member can be rotatable with the housing arrangement.
An embodiment form which is very simple to construct can be achieved when the housing arrangement forms the abutment member.
The present invention will be described more fully in the following with reference to the accompanying drawings.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.